This invention relates to a polymeric sleeve for connecting and/or clamping optical fibers.
Optical fiber connectors that comprise shape memory polymers are known. See U.S. Pat. No. 4,921,323, of Delahanty et al. issued May 1, 1990. In its simplest form, this type of splice connector is a sleeve into which the ends of two fibers are inserted. The sleeve material comprises a shape memory polymer so that when the sleeve is heated, after insertion of the fibers, the sleeve shrinks and effects a splice between the fiber ends. These connectors have several advantages. They are simple and should be relatively inexpensive to manufacture. They are easy to use, and splices can be made quickly and reliably in the field.
The shape memory materials of the prior art are polymers that have some degree of crosslinking. Connector sleeves of these materials are molded with a small bore, smaller than the optical fiber size. The bore is then stretched to a diameter larger than the optical fiber, which creates a semi-permanent condition in the polymer whereby the bore in the polymer sleeve retains the large diameter when the mandrel is removed. This is a metastable state, since the polymer xe2x80x9cremembersxe2x80x9d, and prefers, the shape in which is was molded. However, as long as the sleeve is maintained below its TS it remains in the metastable shape. When the splice is to be made, the optical fibers ends are inserted into the large bore, and the sleeve is heated to shrink the polymer to its molded (memory) shape, thereby gripping the fiber ends and completing the splice. In some cases, heat may be applied to facilitate the stretching step.
Known shape memory polymer materials for optical fiber splice applications are crosslinked polymers. As described in the Delahanty et al. patent references above, they require a minimum crosslinking density to be effective.
We have developed a new class of shape memory materials for optical fiber connector applications. This development follows our finding that non-crosslinked polymers function very effectively as shape memory materials. We have designated this class of materials as Simple Shape Memory Polymers (SSMP). Among the advantages of SSMP materials are that the choice of polymers for optical fiber system applications is expanded. Also expanded are the technologies available for manufacturing the connectors. For example, simple extrusion or injection molding techniques can be employed. Moreover, new approaches to the fabrication of optical fiber splices and other connector elements have been developed for use with this new category of materials.